An increasing number of data centers are being built to satisfy the demands of popular Internet services such as social media, cloud computing and the like. Such data centers include large storage systems, which may include a number of servers, nodes, and a plurality of hard disk drives connected together over a network. Such large storage systems may be scaled linearly. Operations can be shared among all the devices within a large storage system, and may write data to multiple drives or multiple arrays in parallel. As such, one slow hard drive in a large storage system can slow down the performance of the rest of the drives in a system. If a specific problem causing a slow drive is not diagnosed, or in some cases, diagnosed incorrectly, and operations continue, the one slow drive impacts the overall performance of the storage system. Monitoring properties of such large storage systems can allow detection of degradation, failures, and errors in large storage systems.